Amphoteric cellulose and process for the preparation thereof

ABSTRACT

Amphoteric cellulose which contains both cationic and anionic groups linked to the cellulose molecule, and which has an isoelectric point, is prepared. The products can be made to have an affinity for anionic or cationic substances, e.g., acid or basic dyes or resins, by lowering or raising their pH.

United States Patent Elizer [451 July 11,1972

AMPHOTERIC CELLULOSE AND PROCESS FOR THE PREPARATION THEREOF Inventor:Lee H. Ellzer, Keokuk, Iowa Assignee: The Hubinger Company, Keokuk, lowaFiled: Sept. 29, 1969 Appl. No.: 862,051

US. Cl. ..260/212, 8/168, 260/2.1 M, 260/15, 260/17 R, 260/211 R,260/214, 260/215, 260/226, 260/231 A, 260/DIG. 6

Int. Cl. ..C08b 11/00 Field of Search ..260/231 R, 212, 231 A, 226,260/215, 211 R, 214, 2.1 M

Primary Examiner-Donald E. Czaja Assistant Examiner-Ronald W. GriffinAtmrneyJohnston, Root, OKeeffe, Keil, Thompson & Shurtleff 57 ABSTRACTAmphoteric cellulose which contains both cationic and anionic groupslinked to the cellulose molecule, and which has an isoelectric point, isprepared. The products can be made to have an affinity for anionic orcationic substances, e.g., acid or basic dyes or resins, by lowering orraising their pH.

17 Claims, No Drawings AMPHOTERIC CELLULOSE AND PROCESS FOR THEPREPARATION THEREOF BACKGROUND OF THE INVENTION Cellulose, for example,cotton cloth, is normally anionic and substantive to basic dyes. It canbe converted to a cationic form, for example, by the introduction ofcyanamide groups as described in U.S. Pat. No. 3,051,698. The cationicnitrogenated cellulose thus obtained has a direct affinity for acid dyesbut no longer has a direct affinity for basic dyes.

It would be desirable to have a cellulosic material which at a certainpH, known as the isoelectric point, is non-ionic, but can be convertedto a cationic or anionic state by lowering or raising the pH. Such amaterial which has both basic and acidic properties, depending upon thepH conditions, can be called amphoteric.

OBJECTS One of the objects of the invention is to provide new andimproved cellulose derivatives which are amphoteric.

Another object is to provide a process for modifying cellulose so as toproduce a versatile material which is normally non-ionic but can befurther modified by a simple treatment to render it cationic or anionic.

A further object is to produce cellulose having an isoelectric pH whichby pH adjustment can be made to have an affinity for either acid orbasic dyes-or various types of anionic or cationic resins. Other objectswill appear hereinafter.

In accordance with the invention, cellulose is prepared in a form inwhich it contains both cationic and anionic groups.

These new and improved cellulose products are prepared by reactingcellulose with a nitrogen-containing etherifying agent to introduce acationic group into the molecule, for example, one containing aquaternary or tertiary amino group and/or a cyanamide radical, and alsowith a reagent capable of introducing an anionic group into thecellulose molecule, for example, one containing a sulfonic or carboxylicradical.

Preferred nitrogen-containing etherifying agents are 2-chloroethyldiethylamine hydrochloride, also called 2-chlorotriethylamine hydrochloride, and 4-chloro-2-butenyltrimethylammonium chloride having Formulas l and II, respectively, as follows:

\II/ S The reaction with the cellulose can be carried out eithersequentially or simultaneously. Thus, the 2-chloroethyl diethylaminehydrochloride or 4-chloro-2-butenyltrimethyl ammonium chloride can bereacted with the cellulose first, followed by the addition of thepropane sultone or sodium chloroacetate, or the propane sultone orsodium chloroacetate can be reacted with the cellulose, followed by theaddition of the 2-chlorotriethylamine hydrochloride, or 4-chloro-2-butenyltrimethyl ammonium chloride, or the 2-chloroethyldiethylamine hydrochloride and/or 4-chloro-2-butenyltrimethylammonium chloride and the propane sultone and/or sodium chloroacetatecan be mixed together in a suitable solvent to form a clear solutionbefore applying the mixture to the cellulose.

The basic amino groups are preferably introduced into the cellulosemolecule by usingas one of the reactants a tertiary or quaternary amineor amine salt containing a reactive group linked to a hydrocarbon groupof the amine. The hydrocarbon group or groups of the amine can be alkyl(e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl), aryl (e.g.,phenyl, tolyl), aralkyl (e.g., benzyl), or cycloaliphatic (e.g.,cyclopentyl), cyclohexyl, or cycloheptyl). The amine can be a monoamineor a polyamine but is preferably a monoamine. It can also be aheterocyclic amine (e.g., piperidine, pyridine). In general, however,from the standpoint of ease of carrying out the reaction of desirableproperties in the resultant products, it is preferred to use a watersoluble amine. The reactive groups of the amine are preferably eitherhalogen (e.g., chloro-, bromo-, etc.) or epoxy. The portion of the amineto which the reactive group is attached is acyclic. The reactive groupis preferably separated from a nitrogen atom of the amine by at leastone carbon atom, usually two to six carbon atoms.

The resultant products may be described by the following structuralformula:

where X is cellulose, An is an anionic group, e.g., carboxylic,carboxylate, sulfonic, sulfonate, phosphate, phosphonate, or otheranionic group, Cat is cationic group, e.g., tertiary amino, orquaternary, or other amine or amine salt, R and R, are divalent acyclichydrocarbon or hydroxyhydrocarbon groups having 1 to 6 carbon atoms, andm and n represent the number of times these radicals occur, usually aminimum of 0.15 each per l00 anhydroglucose units and a total of m +nnot exceeding l2. The ratio of mm is normally within the range of 1:10to 10:1.

A preferred group of products is represented by the following generalformula:

where X is cellulose, R and R are divalent acyclic hydrocarbon orhydroxyhydrocarbon groups preferably having one to six carbon atoms andmore specifically one to four carbon atoms; R and R are hydrocarbon,preferably alkyl having one to six carbon atoms and more specificallyone to four carbon atoms;

Y is hydrogen or a salt forming radical, e.g., sodium, potassium,calcium, ammonium, and m and n are numerical values representing thenumber of times the anionic and cationic radicals, respectively, occurin the molecule, usually 0.15 to 3, and a total ordinarily not exceeding8, per anhydroglucose units.

The term cellulose" when used herein refers to cellulose in its naturalor regenerated form, e.g., fatty acid esters of cellulose, such ascellulose acetate, cellulose propionate, cellulose butyrate and mixedesters, such as cellulose acetate propionate and cellulose acetatebutyrate, and with cellulose xanthate. The cellulosic material can betreated in any desired physical form, as, for example, in the form of afiber, pulp, or granule slurry, woven or non-woven cloth, paper sheets,or plastic films. The cellulose can be derived from any source such aswood, cotton, straw, pith, and the like. Cellulose xanthate can betreated in solution.

Sultones are intramolecular cyclic esters of hydroxysulfonic acids andmay be derived both from aliphatic and from aromatic sulfonic acids.Examples of sultones suitable for the present purpose arel,3-propanesultone, l,4-butanesultone, mixtures of isomericbutanesultones (which may be prepared from mixtures ofchlorobutanesulfonic acids, obtained by sulfochlorination ofl-chlorobutane), benzylsultone and tolylsultone.

Sodium chloroacetate is the sodium salt of monochloroacetic acid. Thefree acid can be used but since the reaction is carried out underalkaline conditions it will be converted to a salt. Other reactivehalogen aliphatic acids and their salts (e.g., Na, K, Ca) containing twoto six carbon atoms can be used, for example, monobromoacetic acid andits sodium salt, and monochloropropionic acid and its salts.

Examples of amine etherifying agents suitable for the practice of theinvention are: 2-chloroethyldiethylamine; 2- chloroethyldiethylaminehydrochloride; 2-chloroethyldimethylamine; 2-chloroethyldimethylaminehydrochloride; 3-chloropropyldiethylamine; 3-chloropropyldiethylaminehydrochloride; 3-chloropropyldimethylamine; 3-chloropropyldimethylaminehydrochloride; 4-chlorobutyldiethylamine; 4-chlorobutyldiethylaminehydrochloride; 2-chloroisopropyldimethylamine;2-hydroxy-3-chloropropyltrimethylamine chloride;3-dibutylamino-1,2-epoxypropane; 2-bromo-5- diethylaminopentanehydrobromide; N-(2,3-epoxypropyl) piperidine, andN,N-(2,3-epoxypropyl)methyl aniline. ln general, it is preferable to usethe salts of the amine esterifying agents, such as, for example, thehydrochlorides and hydrobromides. Mixtures of amine etherifying agentscan be employed. The salts should be selected so as to avoid formationof precipitates. For example, if calcium, strontium or barium ispresent, sulfates or should not be used because insoluble salts such ascalcium sulfate or calcium phosphate would form. However, sulfates orphosphates can be used where sodium, potassium or lithium ions arepresent.

Cyanamide can be used in an alkaline aqueous solution, preferably of analkali metal or alkaline earth metal base, such as sodium, potassium,lithium, calcium, barium or strontium hydroxide, or their basic salts,or an aqueous solution of an alkali metal or alkaline earth metalcyanamide, such as sodium, potassium or calcium cyanamide. It isordinarily not necessary to add a base to a solution of the cyanamidesalt since solutions of such salts in water are generally sufficientlyalkaline. An aqueous solution of calcium cyanamide, for example,generally has a pH in the range of about 10.5 to 1 1.9. An alkali metalor alkaline earth metal cyanamide hydrolyzes in water to form a solutionwhich is substantially similar to an aqueous solution of cyanamide in analkaline solution of an alkali metal or alkaline earth metal base.

The reaction mixture containing the cellulosic material is maintained atthe desired reaction temperature for a sufficient length of time toobtain the desired degree of substitution. Reaction occurs at asubstantial rate at reduced to ordinary temperatures. This is anadvantage where elevated temperatures are either unfeasible orundesirable. For more rapid reaction rates, the reaction temperature canbe increased. There is ordinarily no economic advantage in continuingthe reaction period beyond the point at which the desired or maximumdegree of substitution is achieved.

The anionic substitution is preferably carried out using a watermiscible organic solvent for the substance used to introduce the anioniccomponent, e.g., acetone, methylethyl ketone, or dimethylformamide. Onereason for dissolving the sultone or other anionic substituent inacetone or other organic solvent is to obtain more even distribution ofanionic groups over the cloth, sheet, or other form of cellulose.Without the solvent or diluent there is a likelihood of producing a highconcentration of anionic groups with the result that a soluble celluloseis formed which dissolves when the product is washed with water. Wherethe product is a cloth, or sheet, holes would be formed in the cloth orsheet. The quantity of solvent required can be determined by routineexperiment. The solution of anionic substituent in the solvent shouldwet the cellulose evenly. The solvent must be chemically inert to thereactants and the product.

KJI

It will be recognized that the quantity of anionic and cationicsubstituents should be controlled to produce a cellulose product havingan isoelectric point which can be made cationic by lowering the pH andanionic by raising the pH.

In the anionic state the cellulose products are substantive to basicdyes, e.g., methylene blue (Cl520l5), and also to cationic treating andcoating compositions including cationic emulsions of urea-formaldehydeand melamine-formaldehyde, and cationic linear polymers containingimino, amino, and quaternary groups, of the type usually referred to ashigh molecular weight polyelectrolytes.

The cellulosic products can be separated from the alkaline reactionmixture, washed, dried, and employed as such at their isoelectricpoints. They can also be acidified to form the cationic acid salts,which, in many cases, are preferred as, for example, where thecellulosic product is to be dyed with an acid dye salt.

The acid salt derivatives can be prepared from the washed and driedproducts by treating them with an aqueous solution of the desired acid.Ordinarily, they are most conveniently prepared by acidification of thealkaline reaction mixture with the particular acid, the derivative ofwhich is desired. The pH is preferably reduced to 4 or less, in somecases, to as low as l.

Substantially any acid can be used, including inorganic and organicacids, such as hydrochloric, nitric, sulfuric, sulfurous, phosphoric,acetic, propionic acids, and the like. In general, it is preferred toemploy hydrochloric acid.

The acidification treatment can be carried out at reduced, ambient orelevated temperatures, as, for example, the temperature of the initialsubstitution reaction. After the acid treatment is completed, thecellulose product acid salts can be removed from the reaction mixture,washed, and dried in any convenient manner.

The derivatives in the cationic state possess the dyeing properties ofwool and can readily by dyed with acid dyestuffs such as light green SFyellowish (C.l. 670, Merck Index, 6th Edition, page 573), acid fuchsine(CI. 692, trisodium salt of the trisulfonic acid of parafuchsine), eosinY (C.l. 7 68, disodium salt of2,4,5,7-tetrabromo-9-0-carboxyphenyl-6-hydroxy- 3-isoxanthone), orange G(O1. 27, disodium salt of l-phenylazo-2-naphthol-6,8-disulfonic acid),and the like.

The cellulose derivatives in the cationic state are also substantive toanionic treating and coating compositions, such as anionic emulsions ofurea-formaldehyde, melamine-formaldehyde, polystyrene, acrylic resins,vinyl resins, rubber, rosin, and the like. Starch sizing is alsoimproved.

The reagents for introducing anionic and cationic groups both act asetherifying agents for cellulose under basic conditions. The reactioncan be carried out at ordinary or slightly elevated temperatures belowthe temperature at which the cellulose is degraded, for example, withinthe range of 35 to 225 F. The reaction can be carried out underatmospheric, subatmospheric or superatmospheric pressures. The productis insoluble in water and therefore can be recovered by filtration,washing with water and drying.

The invention will be further illustrated but is not limited by thefollowing examples in which the quantities are stated in parts by weightunless otherwise indicated.

EXAMPLE 1 Dissolve 183 grams (1.5 moles) propane sultone in 174 grams (3moles) acetone. Apply this solution evenly and uniformly to a strip ofbleached, unfinished cotton sheeting weighing 81 grams (0.5 AGU) drysubstance cellulose.

Dissolve 258 grams (1.5 moles) 2-chloroethyldiethylamine hydrochloridein cc (5 moles) of water. Apply this solution to the aforesaid cloth.

Dissolve grams (4.5 moles) of NaOH in 180 grams (10 moles) of water.Cool to ambiency (78 F.) Apply this alkaline solution to the previouslytreated cloth uniformly and allow the cloth to remain submergedcompletely for 22 hours, at which time the pH is 10.5. It should benoted that the temperature rises to 101 C. when the NaOH is added.

lnInAA (V114 EXAMPLE I] Dissolve 122 grams (1 mole) of propane sultonein 87 grams (1.5 moles) of acetone. Apply this solution to 81 grams ofbleached unfinished cotton sheeting as in Example 1. Dissolve 172 grams(1 mole) of 2-chloroethyldiethylamine hydrochloride in 45 grams (2.5moles) of water and apply this solution to the cotton sheeting.

Dissolve 120 grams (3 moles) NaOH in 120 cc of water and apply thissolution to the cotton sheeting. The temperature rises to 101 C. Leavethe cotton sheeting submerged for 22 hours. The pH is 10.6 and isadjusted to 7 by adding 119 cc 6N HCl. Wash the product well with tapwater and finally in distilled water. Allow it to air dry. This producthas an isoelectric pH of6.06.5. This product was labeled 7.235.

EXAMPLE Ill Dissolve 61 grams (0.5 mole) of propane sultone in 87 gramsmoles) of acetone. Apply this solution evenly to 81 grams of bleachedunfinished cotton sheeting.

Dissolve 86 grams (0.5 mole) of 2-chloroethyldiethylamine hydrochloridein 23 cc of water. Apply this solution evenly to the cotton sheeting.

Dissolve 60 grams (1.5 moles) of NaOH in 60 cc of water. Cool toambiency (78 F.) and apply this solution evenly to the cotton sheeting.The temperature rises to 76 C. Add 200 cc of water and keep the clothsubmerged in the solution for 21 hours. At the end of this time the pHis l 1. Adjust the pH to 7 by adding 80 cc of 6N HCl. Wash the productwell with tap water and finally in distilled water. Allow it to air dry.This product has an isoelectric pH of 65-75. This product was labeled7.3-35.

EXAMPLE lV Dissolve 30.5 grams (0.25 mole) of propane sultone in 87grams 1.5 moles) of acetone. Apply this solution evenly to 81 grams (0.5AGU) of bleached unfinished cotton sheeting.

Dissolve 43 grams (0.25 mole) of 2-chloroethyldiethylamine hydrochloridein 12 cc of water and apply this solution to said cotton sheetingevenly.

Dissolve 30 grams (0.75 mole) of NaOH in 30 cc of water, cool to 78 F.and apply this solution of the cotton sheeting evenly. Add 500 cc ofwater and keep the cotton sheeting submerged for 21 hours. Thetemperature rises to 36 C. The pH is 11.3.

At the end of2l hours, adjust the pH to 7 by adding 25 cc of 6N HCL.Wash the cellulose product well with tap water and finally withdistilled water. This product has an isoelectric pH of 6.5-7.5. It islabeled 7.4-35.

EXAMPLE V Dissolve 6.1 grams (0.05 mole) of propane sultone in 87 gramsof acetone and apply the solution to 81 grams of bleached unfinishedcotton sheeting.

Dissolve 8.6 grams (0.05 mole) of 2-chloroethyldiethylaminehydrochloride in 12 cc of water and apply this solution to said cottonsheeting evenly.

Dissolve 6 grams (0.15 mole) of NaOH in 12 cc of water, cool and wet thecotton sheeting evenly with this solution. Add 500 cc of water, keepsubmerged for 18 hours at the am bient temperature (78 F.). After 18hours the pH drops from 11.6 to 9.2. Add 13 cc of 6N HCl to adjust thepH to 7.0. Wash the product well with tap water, then with distilledwater and air dry it. This product has an isoelectric pH of 6.0-7.5. Itis labeled 75-35.

The products in Examples 1 to V were analyzed and compared with a blankof the bleached unfinished cotton sheeting with the results shown in thefollowing table.

TABLE OvenDry Blank 7.1-35 7.2-35 7.3-35 7.4-35 7.5-35 Solids (percent)95.16 90.90 92.04 93.94 92.58 94.32 Ash%Dry basis 0.49 0.64 0.66 0.350.19 0.09 Nitrogen% Drybasis 0.04 0.59 0.67 0.67 0.57 0.16 Sulfur%Drybasis 0.006 0.91 1.02 0.64 0.64 0.10 isoelectric pH 6.0-6.5 6.0-6.56.5-7.5 (1.5-7.5 6.0-7.5

It will be seen that all of these products when compared to the blankshowed an appreciable increase in nitrogen and sulfur contents. All ofthem had an isoelectric pH, whereas the blank had no isoelectric pH. Allof them could be rendered either cationic or anionic by lowering orraising the pH from the isoelectric pH.

The following method is used in obtaining the isoelectric pH:

Suspend a strip of cloth about one inch wide and 10 inches long in 500cc distilled water. Adjust the pH to 4.0 with 0.1N HCl. When the pHbecomes constant at 4.0 (this may take 10 minutes) remove cloth, squeezeand place in about 10 cc of 0.0001 molar light green SF yellowish, C.I.No. 42095. If the cloth takes all the dye out of the solution, which7.1-35, 7.2-35, 7.3-35, 7.4'35, and 7.5-35 did, another strip of clothis immersed in 500.0 cc water at pH 4.5 and the dyeing repeated, and soon in steps of 0.5 pH unit until the cloth does not accept the acid dye.7.1-35 did not accept the acid dye, light green SF yellowish at pH 6.0,although it did accept it at pH 5.5, therefore, 7.135 is cationic belowpH about 6.0. Another strip was immersed in about 500 cc distilled waterand the pH adjusted to 9.0 with 0.1N KOH. When the pH became constantafter about 10 minutes, the strip of cloth was squeezed and immersed in0.0001 molar solution of the basic dye methylene blue, C]. No. 52015;after about 3 minutes there was no dye in 7.1-35, 7.2-35, 7.3-35, 7.4-35and 7.535 solutions, so the process was repeated at pH 8.5, then 8.0,etc. until the dye remained in the solution. Therefore, above pH 6.5,the cloth labeled 7.1-35 is anionic. The isoelectric pH is between 6.0and 6.5; below pH 6.0 the cloth is cationic and above pH 6.5, it isanionic. The bleached sheeting used in these experiments was anionic atall pH s.

In a similar manner to the examples, a series of cellulose productscontaining carboxy and carboxylate substituents instead of sulfonic andsulfonate substituents can be prepared by substituting chemicallyequivalent amounts of sodium chloroacetate for the sulfone. Othercationic substituents can be added to the cellulose molecule bysubstituting other amines as previously given, or cyanamide, for the 2-chloroethyldiethylamine, in chemically equivalent amounts. Specificallypreferred are 4-chloro-2-butenyltrimethyl ammonium chloride and2-hydroxy-3-chloropropyltrimethylamine chloride.

The cationic groups which are introduced into the cellulose molecule arepreferably tertiary amino groups or quaternary amino groups but can beof any other type. The introduction of the anionic groups into thecellulose molecule can take place with the elimination of a hydrogenhalide. For example, where sodium chloroacetate is employed the reactionoccurs with the elimination of hydrogen chloride. 1n the case of propanesultone the reaction takes place with the opening of the sultone ring.

The isoelectric cellulose has enhanced oil resistance and enhancedresistance to ink penetration. It is therefore especially useful forpaper, cloth, and other non-woven and woven sheet materials. Theproducts of the invention are also useful as ion exchange materials andin making ionic membranes and dialysis membranes. In the textile field,the invention is very useful in increasing the affinity of cellulose, ormixtures of cellulose and polyester fibers (e.g., 65 percent polyesterfiber and 35 percent cotton fibers), for specific types of dyes.

The invention is hereby claimed as follows:

1. Cellulose having the formula [AnR,],,,-X[0-R-Cat],,

wherein X is cellulose, An is an anionic group, Cat is a cationic group,R and R, are divalent acylic hydrocarbon or hydroxyhydrocarbon groupshaving one to six carbon atoms, m and n are each at least 0.15 per 100anhydroglucose units, the total of m n does not exceed 12 per lOOanhydroglucose units, and the ratio of mrn is within the range of 1:10to l0: 1.

2. A cellulose as claimed in claim 1 in which An is carboxylic orcarboxylate.

3. A cellulose as claimed in claim 1 in which An is sulfonic orsulfonate.

4. A cellulose as claimed in claim 1 in which Cat is quaternaryammonium.

5. A cellulose as claimed in claim 1 in which Cat is tertiary amino.

6. A cellulose as claimed in claim 1 in which Cat is cyanamidc.

7. Cellulose having the formula where X is cellulose, R and R aredivalent acyclic hydrocarbon or hydroxyhydrocarbon groups having one tosix carbon atoms, R and R are hydrocarbon having one to six carbonatoms,

Y is hydrogen or a salt forming radical, m and n are numerical valueshaving a minimum value of 0.]5 per I00 anhydroglucose units, the totalof m n not exceeding 12 per I00 anhydroglucose units and the ratio ofm:nbeing within the range oflzlOto l0:].

8. A cellulose as claimed in claim I in which the pH is its isoelectricpH.

9. A cellulose as claimed in claim 1 which has its pH lowered below theisoelectric pH.

10. A cellulose as claimed in claim 1 which has its pH raised above theisoelectric pH.

11. A process for preparing an amphoteric cellulose which comprisesreacting cellulose in an alkaline medium with a cationic nitrogencontaining etherifying agent and a reagent containing anionic groupscapable of reacting with the cellulose to form an ether of the cellulosein which an oxygen atom of the cellulose is connected through ahydrocarbon group to an anionic group, said reagent being dissolved in awater miscible organic solvent which is chemically inert to thereactants and product and is present in sufficient amount to distributeand reagent uniformly in contact with the cellulose, the quantities ofsaid nitrogen containing etherifying agent and said reagent containinganionic groups being sufficient to produce an amphoteric cellulose butinsufficient to render the cellulose water soluble.

12. A process as claimed in claim ll in which said reagent is amonohalogeno carboxylic acid containing 1 to 6 carbon u a 13. A processas claimed in claim 11 m WhlCh said reagent is a sultone.

14. A process as claimed in claim 11 in which said reagent is sodiumchloroacetate.

15. A process as claimed in claim 11 in which said reagent is propanesultone.

16, A process as claimed in claim 11 in which the ratio of anionicgroups to cationic groups in the amphoteric cellulose is within therange of 1:10 to 10:1.

17. A process as claimed in claim 11 in which the proportions ofreactants are sufficient to introduce a minimum of 0.15 anionic group,0.15 cationic group and a total not exceeding l2 anionic and cationicgroups per anhydroglucose units in the cellulose.

mg UNITED STATES PATENT OFFICE CERTIFICATE-OF CORRECTIN Patenr No. ,423Dated Jul 11, 1972 Inventofls) Lee H. Elizer V 1 It. is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below: v

. "I Column 8, line, 20, claim 11, "-to distribute-and" should read toidis tributei 'said I 1 Signed ana seel'edthie lzt fda or December 1972.

(SEAL) Attest: I

EDWARD M.FLETCHER,JR. I ROBERT GUTTSCHALK Attesting Officer vCommissioner of-Patents

2. A cellulose as claimed in claim 1 in which An is carboxylic orcarboxylate.
 3. A cellulose as claimed in claim 1 in which An issulfonic or sulfonate.
 4. A cellulose as claimed in claim 1 in which Catis quaternary ammonium.
 5. A cellulose as claimed in claim 1 in whichCat is tertiary amino.
 6. A cellulose as claimed in claim 1 in which Catis cyanamide.
 7. Cellulose having the formula where X is cellulose, Rand R1 are divalent acyclic hydrocarbon or hydroxyhydrocarbon groupshaving one to six carbon atoms, R2 and R3 are hydrocarbon having one tosix carbon atoms, Y is hydrogen or a salt forming radical, m and n arenumerical values having a minimum value of 0.15 per 100 anhydroglucoseunits, the total of m + n not exceeding 12 per 100 anhydroglucose unitsand the ratio of m:n being within the range of 1:10 to 10:
 8. Acellulose as claimed in claim 1 in which the pH is its isoelectric pH.9. A cellulose as claimed in claim 1 which has its pH lowered below theisoelectric pH.
 10. A cellulose as claimed in claim 1 which has its pHraised above the isoelectric pH.
 11. A process for preparing anamphoteric cellulose which comprises reacting cellulose in an alkalinemedium with a cationic nitrogen containing etherifying aGent and areagent containing anionic groups capable of reacting with the celluloseto form an ether of the cellulose in which an oxygen atom of thecellulose is connected through a hydrocarbon group to an anionic group,said reagent being dissolved in a water miscible organic solvent whichis chemically inert to the reactants and product and is present insufficient amount to distribute and reagent uniformly in contact withthe cellulose, the quantities of said nitrogen containing etherifyingagent and said reagent containing anionic groups being sufficient toproduce an amphoteric cellulose but insufficient to render the cellulosewater soluble.
 12. A process as claimed in claim 11 in which saidreagent is a monohalogeno carboxylic acid containing one to six carbonatoms.
 13. A process as claimed in claim 11 in which said reagent is asultone.
 14. A process as claimed in claim 11 in which said reagent issodium chloroacetate.
 15. A process as claimed in claim 11 in which saidreagent is propane sultone.
 16. A process as claimed in claim 11 inwhich the ratio of anionic groups to cationic groups in the amphotericcellulose is within the range of 1:10 to 10:1.
 17. A process as claimedin claim 11 in which the proportions of reactants are sufficient tointroduce a minimum of 0.15 anionic group, 0.15 cationic group and atotal not exceeding 12 anionic and cationic groups per 100anhydroglucose units in the cellulose.